This description relates to fluid droplet ejection. In some fluid ejection devices, a substrate includes a fluid pumping chamber, a descender, and a nozzle. Fluid droplets can be ejected from the nozzle onto a medium, such as in a printing operation. The nozzle is fluidly connected to the descender, which is fluidly connected to the fluid pumping chamber. The fluid pumping chamber can be actuated by a transducer, such as a thermal or piezoelectric actuator, and when actuated, the fluid pumping chamber can cause ejection of a fluid droplet through the nozzle. The transducer can be actuated by a voltage applied by a trace that electrically connects the transducer to a voltage source, such as an application-specific integrated circuit (ASIC). The medium can be moved relative to the fluid ejection device. The ejection of a fluid droplet from a nozzle can be timed with the movement of the medium to place a fluid droplet at a desired location on the medium. Fluid ejection devices typically include multiple nozzles, and it is usually desirable to eject fluid droplets of uniform size and speed, and in the same direction, to provide uniform deposition of fluid droplets on the medium.